help me, I got one negative feedback, how can I do.

I got one negative feedback on Ebay, because this item I bought insurance, and have a track number,the USPS showed the buyer received it, but she said she didn't received it, she asked me refund her money, andshe opened solved, the paypal hold my money, today the paypal back my money to my account, the buyer give me the negative feedback, how can I add explain to her negative feedback.

many thanks